Unfolded Protein Response (UPR) Induced Hybrid Promoters for Heterologous Gene Expression in Pichia pastoris

Abstract

Inducible promoters constitute a powerful tool in controlling gene expression of heterologous proteins in Pichia pastoris. To expand a native promoter activity, we created an inducible hybrid promoter consisting of a constitutive transcription elongation factor 1 (TEF1) promoter (PTEF1) and a 22-bp multimer of unfolded protein response element (UPRE) from Saccharomyces cerevisiae KAR2 gene. The four copies of the UPRE sequence were located immediately upstream to the PTEF1. The activity of the hybrid promoter for driving expression of green fluorescent protein (GFP) was three to four times higher than its native counterpart without any chemical supplement. Upon adding dithiothreitol (DTT) supplement, the promoter activity increased an additional three-fold within nine hours. The activity was also effective with recombinant human erythropoietin (EPO) expression. Hence this platform may have applications in metabolic engineering, where it can be used as an alternative system for fine-tuning gene expression of heterologous protein in P. pastoris.